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    RE: iSCSI: response to second login (with same ISID)



    > I'd vote for (2) for the following reasons :
    > 
    > a) It is possible for initiators to use the ISID as a scheme to
    > establish persistence of their O.S. device files. In doing so,
    > initiators would attempt to obtain the same ISID for a given 
    > session to
    > a given target ports across boots. (and rightly so, for 
    > enabling targets
    > to track persistent reservation like properties, etc).
    > 
    > In the event where the initiator went through a non-orderly shutdown
    > which did not close all sessions, it would attempt to re-login on
    > re-boot with the same ISID. If the target rejected this re-login, per
    > (1) (citing an invalid ISID), the initiator would no longer be able to
    > maintain persistence of the session to an ISID.
    > 
    > b) Using (2) allows the hosts to hint to the target that the previous
    > session is now stale and thus triggers clean-up of stale session
    > resources.
    
    This seems to me to provide another example why ISID should *not* be used
    for persistent reservation re-establishment.  It's ambiguous whether this is
    a case of "defective initiator" or "initiator trying to re-claim persistent
    reservations" and there is no way for iSCSI to resolve this question.  Since
    persistent reservations are SCSI layer things, lets try to find a way to
    keep their implementation from forcing unnecessary limitations at the iSCSI
    layer.  The use of init. name+ISID+target name for identifying persistent
    reservations needs further discussion before we allow it to creep into iSCSI
    protocol rules.  I've very uncomfortable with treating ISID like a fixed
    address just because SCSI persistent reservations don't have a sufficient
    SCSI layer mechanism.  Seems like this will force all kinds of layering
    violations into iSCSI.
    
    Marj
    


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Last updated: Tue Sep 04 01:04:39 2001
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